ENGIN. 
LIBRARY 


r-NRLF 


11D 


ESTIMATING 
CONCRETE 
BUILDINGS 

C  L  A  Y  T  O  N    W       M  A  YE  R  S 


IT) 
00 
CM 

CO 


UNIVERSITY  OF  CALIFORNIA 

DEPARTMENT  OF  CIVIL   ENGINEERING 

BERKELEY.  CALIFORNIA 


Engineering 


UNIVERSITY  OF  CALIFORNIA 

DEPARTMENT  OF  CIVIL.  ENGINEERING 

BERKELEY.  CALIFORNIA 


ESTIMATING 

CONCRETE 

BUI  LDINGS 


By 

CLAYTON  W.  MAYERS 

it 


(Price,  $1.00) 


PUBLISHED  BY 

ABERTHAW  CONSTRUCTION  COMPANY 

BOSTON,  MASSACHUSETTS 

1920 


/V)3 


Engineering: 
Library 


Engineering 
Library 


Copyright,  1920 

by 
Aberthaw  Construction  Company 


PREFACE 

process  of  building,  in  the  time-honored  accepta- 
tion of  the  term,  consists  of  the  assembling  of  units 
already  manufactured,  and  the  fitting  of  them  into 
their  appointed  places.  Methods  of  accomplishing  these 
things  have  been  developed  through  the  successive  experi- 
ence of  generations  of  builders  until  they  have  crystallized 
into  a  traditional  practice  the  cost  of  which  may  be  pre- 
judged with  reasonable  accuracy. 

Concrete  construction,  on  the  other  hand,  is  less  a  process 
of  building  than  it  is  of  manufacturing.  Cement,  sand,  stone, 
water  and  steel  are  brought  together  under  conditions  which 
produce  a  chemical  action  that  fuses  these  elements  into  a 
whole  quite  different  from  the  sum  of  its  constituent  parts. 
The  consideration  that  this  occurs  on  the  spot  where  the 
unit  produced  is  to  remain  as  part  of  the  finished  structure, 
in  no  wise  alters  the  essential  fact  that  the  process  is  one 
of  manufacture.  The  traditional  operations  of  the  builder 
come  into  play  mainly  in  the  placing  of  subsidiary  orsubordi- 
nate  units,  and  in  supplying  necessary  fittings. 

The  actual  procedure  of  concrete  construction  is  still  very 
far  from  approximating  standard  practice.  Still  less  has  there 
emerged  any  generally  accepted  system  for  keeping  track 
of  the  individual  cost  of  the  innumerable  items  that  enter 
into  this  type  of  work.  Hence  no  satisfactory  basis  has  been 
supplied  for  making  estimates  in  advance  of  the  actual 
undertaking. 

Estimates  are  made,  of  course;  but  in  the  great  majority 
of  instances  they  are  little  more  than  the  shrewd  guess  of 
one  whose  cost  instinct  has  been  sharpened  by  experience. 
Few  are  the  estimators  of  concrete  construction  whose  com- 
putations follow  any  scientific  plan,  or  whose  results  are 
capable  of  analysis.  Indeed,  it  may  be  said  of  estimators, 
as  of  poets,  that  they  are  seldom  able  to  explain  their  figures 
once  these  have  been  allowed  to  cool. 

800362 


The  nature  of  the  special  responsibility  which  the  Aber- 
thaw  Construction  Company  has  assumed  in  the  field  of 
building  has  necessitated  the  evolution  of  a  highly  exact 
system  of  cost  accounting.  Upon  this,  in  turn,  it  has  been 
possible  to  establish  similarly  thorough-going  methods  of 
drafting  estimates.  Years  of  study  have  at  length  produced 
a  satisfactory  Company  practice,  which  Mr.  Mayers  has  so 
clearly  outlined  in  his  treatise  that  it  has  seemed  well  worth 
while  to  publish  it.  It  should  prove  an  authoritative  text, 
helpful  alike  to  students  and  to  practitioners  of  concrete 
construction. 

ABERTHAW  CONSTRUCTION  COMPANY 


Boston,  January,  1920. 


ESTIMATING  CONCRETE 
BUILDINGS 

INTRODUCTORY 

MAKING  an  estimate  for  a  reinforced  concrete  build- 
ing involves  much  more  labor  than  is  required  in 
that  for  buildings  constructed  of  structural  steel, 
brick,  wood  or  a  combination  of  these  materials.  This  becomes 
obvious  when  we  consider  that  a  reinforced  concrete  beam 
is  composed  of  certain  quantities  of  cement,  sand,  crushed 
stone,  water,  reinforcement,  form  work  and  labor,  whereas 
a  steel  I  beam  in  place  in  a  building  represents,  insofar  as 
we  are  concerned,  only  a  certain  amount  of  structural  steel 
and  labor. 

In  order  to  estimate  the  cost  of  a  reinforced  concrete 
beam,  column,  floor  slab  or  wall  it  is  necessary  to  determine 
the  quantities  of  concrete,  steel  reinforcement,  form  work 
and  labor  involved,  and  to  these  quantities  affix  proper 
unit  prices.  In  arriving  at  proper  unit  prices,  we  must  still 
further  sub-divide  the  amount  of  concrete  into  its  constitu- 
ent parts  of  cement,  sand  and  crushed  stone.  We  must  like- 
wise determine  the  amount  of  lumber  necessary  properly 
to  form  the  concrete,  before  a  correct  unit  price  for  form  work 
may  be  decided  upon.  Again,  the  necessary  amount  of  plant 
equipment,  and  the  labor  incidental  to  its  installation  and 
removal,  must  be  carefully  considered  and  the  cost  deter- 
mined before  the  estimate  is  complete. 

Compare  with  this  the  process  of  estimating  the  cost  of 
a  steel  member  in  a  building,  which  consists  of  so  many 
pounds  of  steel  and  so  much  labor,  and  we  may  readily 
appreciate  that  accurately  to  estimate  all  the  structural 
members  of  a  reinforced  concrete  building  requires  much 
more  detail  work  than  is  called  for  in  estimating  most 
other  types  of  building  construction. 


PART  I 
QUANTITIES 

I.    GENERAL  PROCEDURE 

Scaling 

In  estimating  the  cost  of  a  reinforced  concrete  building, 
it  is  essential  to  make  a  complete  list  of  all  materials  and 
labor  arranged  in  a  convenient  form,  in  accordance  with 
methods  which  will  involve  the  least  amount  of  labor.  In 
making  this  list,  it  is  necessary  to  consider  every  structural 
member  in  the  building  from  the  footings  to  the  roof  slab. 
The  quantities  will  be  determined  by  carefully  scaling,  or 
making  a  quantity  survey  of  the  plans  of  the  proposed 
building.  The  estimated  quantities  will  then  be  priced;  and 
the  sum  of  the  extended  totals,  to  which  have  been  added 
the  cost  of  superintendence,  liability  insurance,  profit  and 
other  items  common  to  all  building  operations  will,  if  cor- 
rectly figured,  closely  approximate  the  final  cost  of  the  work. 

Stationery  Forms 

Making  a  scaling  of  the  plans,  as  it  is  commonly  called, 
is  the  first  step  in  preparing  an  estimate.  In  order  to  per- 
form this  work  rapidly  and  with  the  least  possible  chance 
for  error,  properly  ruled  stationery  is  essential.  Paper 
(8>£  inches  x  11  inches)  ruled  like  the  copy  shown  below 
has  been  found  of  convenient  design.  Its  use  is  recommended. 


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Column  No.  1  is  the  description  column.  It  is  used  to  note 
briefly  the  location  and  character  of  the  work  being  scaled 
in  order  that  future  identification  may  easily  be  made. 

Column  No.  2  is  the  times  column.  In  this  column  should 
be  noted  the  number  of  pieces  or  duplicate  members  which 
are  being  scaled  from  the  plans,  as  exactly  alike.  If  no  dupli- 
cate pieces  are  shown  on  the  drawing,  this  column  is  not 
used  and  it  is  understood  that  but  one  member  or  unit  is 
to  be  estimated. 

Column  No.  3  is  the  first  dimension,  or  length,  column. 


Estimating  Concrete  Buildings  1 

Column  No.  4  is  the  second  dimension,  or  width,  column. 

Column  No.  5  is  the  third  dimension,  or  height,  column. 

Column  No.  6  is  the  quantity  column,  and  should  contain 
the  extended  quantity  only. 

Column  No.  7  is  the  summary  column,  in  which  the  total 
of  the  quantity  column  is  shown  reduced  to  the  unit  of 
measure  generally  accepted  as  the  standard  measure  ready 
for  pricing;  —  as  cubic  yards  of  concrete,  tons  of  steel 
reinforcement,  etc. 

Column  No.  8  is  for  the  unit  price. 

Column  No.  9  is  the  total  column,  for  the  product  obtained 
by  multiplying  the  summarized  quantity  by  the  unit  price. 
This  product  is  carried  out  in  even  dollars. 

The  Order  of  Scaling 

On  account  of  the  comparatively  large  number  of  details 
involved  in  estimating  the  cost  of  reinforced  concrete  con- 
struction, it  is  important  that  a  definite  system,  or  order  of 
scaling,  be  laid  out  and  carefully  followed.  When  this  is 
done,  the  work  of  scaling  the  plans  is  greatly  simplified  and 
the  liability  to  error  is  reduced  to  a  minimum.  In  preparing 
the  list,  or  order  of  scaling,  the  items  to  be  scaled  should, 
with  one  or  two  exceptions  mentioned  later  on,  be  con- 
sidered in  the  order  of  actual  job  construction.  For  the 
convenience  of  the  reader,  a  list  is  given  below  which  fulfills 
this  requirement  and  is  easily  remembered. 

AREA  AND  CUBE 

CONCRETE 

Exterior  and  interior  footings 

Foundation  walls 

Exterior  columns  and  brackets 

Interior  columns  and  heads 

Floor  slabs  and  roof  slab 

Drop  panels 

Wall  beams,  parapet  beams,  and  curtain  walls 

Interior  floor  beams 

Partitions 

Window  sills  (including  forms  and  reinforcement) 

Copings  (including  forms  and  reinforcement) 

Stairs  and  stair  landings  (including  forms  and  reinforcement) 

Paving 

Granolithic  finish 

Carborundum  rubbing 


Estimating  Concrete  Buildings 


FORMS 

Exterior  and  interior  footings 

Foundation  walls 

Exterior  columns  and  brackets 

Interior  columns  and  heads 

Floor  slabs  and  roof  slab 

Drop  panels 

Wall  beams,  parapet  beams,  and  curtain  walls 

Interior  floor  beams 

Partitions 

Window  sills,  copings,  stairs  and  landings,  etc. 
REINFORCEMENT 

(See  list  for  forms) 
EXCAVATION 

General  or  steam  shovel 

Hand  work 

Backfill 

Sheeting 
MASONRY 

Brick  work 

Brick  veneer 

Terra  cotta  partitions 

Plastering 
STEEL  SASH 
GLASS  AND  GLAZING 
DOORS,  FRAMES,  HARDWARE,  ETC. 
LIGHT  IRON  WORK  AND  MISCELLANEOUS  IRON 
ROOFING  AND  FLASHING 
PAINTING 

Walls  and  ceilings 

Sash  and  doors 

Light  iron 

ENGINEERING,  PLANS,  ETC. 
CLEAN  UP  JOB  AT  COMPLETION 
LIABILITY  INSURANCE 
WATCHMAN 
SUPERINTENDENCE,  JOB  OVERHEAD,  OFFICE,  STATIONERY,  TELEPHONE, 

ETC. 

SUNDRIES 
PROFIT 

This  list  is  by  no  means  exhaustive  but  it  will  serve  as 
a  sufficient  outline,  which  may  be  elaborated  tiy  the  addition 
of  special  items  as  they  occur.  As  it  stands,  however,  the 
list  includes  the  items  usually  found  in  a  typical  reinforced 
concrete  building. 

The  proper  method  of  scaling  the  quantities  in  each 
element  of  the  list  as  given  is  briefly  discussed  in  the  pages 
which  follow. 


Estimating  Concrete  Buildings  9 

II.    PRELIMINARIES 

Area  and  Cube 

Preliminary  to  any  estimate  for  a  building  there  should 
be  noted  the  square  foot  area  of  the  floors  of  the  building 
and  the  cubical  contents  of  the  structure. 

This  is  done  in  order  that  the  estimator  may,  with  practice, 
learn  to  judge  the  cost  of  the  work  quite  closely  on  a  square 
and  cube  foot  basis  before  the  estimate  is  begun.  Practice 
of  this  kind,  checked  up  after  the  estimate  is  completed, 
will  be  very  helpful  in  developing  the  estimator's  judgment*- 

In  determining  the  area,  the  floors  (including  basements) 
should  be  measured  and  the  dimensions  taken  "out  to  out." 
For  instance,  the  area  of  a  building  two  stories  high,  160 
feet  long  and  60  feet  wide  should  appear  on  the  estimate 
sheet  as  follows:  —  2  x  160  x  60  equals  19,200  square  feet. 

The  cubical  contents  of  the  building  should  be  figured 
from  the  same  length  and  width  dimensions;  the  total 
height  being  measured  from  the  bottom  of  the  basement 
floor  to  the  top  of  the  roof  slab.  The  cubical  contents,  or 
cube,  as  it  is  commonly  called,  should  then  appear  as 
follows:  —  160  x  60  x  23f  equals  227,200  cubic  feet. 


III.     CONCRETE 

Concrete  Exterior  and  Interior  Footings 


Founfcfion  IYsf(l 
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1 


Exfer/or  roofings 
I  A  to  9A  incf. 
I&-9&.  /C-9C 
ID  to  3D  incl. 

FIG.  1 


5  '-10" 

Interior  Footings  f/-3-6  Mix) 


FIG.  2 


10 


Estimating  Concrete  Buildings 


In  scaling  the  quantities  of  a  concrete  footing,  it  is 
necessary  first  to  determine  the  amount  of  concrete  in  the 
footing  by  tabulating  in  the  proper  column  of  the  estimate 
sheet  the  dimensions  of  the  footing. 

For  example,  Fig.  1  represents  one  of  twenty-two  typical 
exterior  column  footings  for  a  reinforced  concrete  building. 

First  describe  the  footings  in  column  No.  1  as  follows: 

Footing  No.  1A  to  9A  inclusive,  IB  and  9B,  1C  and  9C, 
ID  to  9D  inclusive.  Next  in  column  No.  2  note  the  number 
of  footings  which  are  alike  (in  this  case  22).  In  the  length 
column  note  the  length  of  the  lower  block  (5#  feet),  follow- 
ing with  the  width  and  height  dimensions  (4^  feet  and  l£ 
feet,  respectively).  Thus  the  concrete  contained  in  the  lower 
blocks  of  these  22  footings  is  tabulated  as  22  x  5y£  x  4^  x 

i*. 

On  the  line  below  tabulate  the  upper  block  of  the  footings, 
which  will  appear  22x4x2^x1.  The  scaling  of  the 
quantities  in  the  interior  footings  (Fig.  2)  is  handled  in  the 
same  way  and,  when  properly  tabulated  on  the  estimate 
sheet,  appears  as  follows :  — 


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This  completes  the  scaling  of  the  concrete  in  the  footings. 
It  will  not  be  necessary  to  refer  to  the  plans  again  in  order 
to  get  the  form  quantities  in  connection  with  these  footings. 
This  will  be  explained  later  on  in  the  section  under  Form- 
work. 

It  will  be  noted  that  fractions  are  used  instead  of  inches 
or  decimal  parts  of  a  foot.  To  use  inches  makes  extension 
of  totals  difficult  and  the  tabulation  unwieldy.  To  use 
decimals  is  to  invite  error,  as  the  decimal  point  is  very 
likely  to  be  misplaced  or  omitted.  Years  of  practice  have 
proved  that  the  only  safe  method  is  to  use  fractions  of  a 
foot  when  inches  are  indicated;  no  fraction  to  be  smaller 
than  one-twelfth  (£%). 

Thus:  — 

3  feet  5  inches  =  3^  feet 
6  feet  9  inches  =  Q^  feet 
8  feet  10  inches  =  8f  feet 


Estimating  Concrete  Buildings  11 

Where  half  inches  are  involved  in  concrete  work  (except  in 
the  thickness  of  floors),  the  fraction  should  be  equivalent 
to  the  next  higher  even  inches.  For  example:  — 

6  feet  5y£  inches  =  6>£  feet 

7  feet  2K  inches  =  7^  feet 

This  ruling  can  be  safely  followed  without  danger  of  gross 
error  except  in  the  case  of  floor  thickness,  which  will  be 
discussed  under  Concrete  Floor  Slabs. 

As  all  hand  books  show  the  weights  of  steel  bars  in  deci- 
mal parts  of  a  pound,  it  will  be  necessary  to  use  decimals 
in  computing  the  tonnage  of  steel  reinforcement. 

The  slide  rule  will  be  found  of  great  value  in  extending 
quantities,  and  its  intelligent  use  will  result  in  both  speed 
and  accuracy.  All  arithmetical  computations  should  be 
checked  by  a  second  person  before  the  estimate  is  submitted. 

Certain  abbreviations  are  generally  used  to  simplify  the 
scaling  of  reinforced  concrete.  In  these  it  will  be  found  that 
reversing  the  order  of  the  letters  in  some  of  the  abbrevia- 
tions reduces  the  liability  to  errors  due  to  mistaking  care- 
lessly made  letters  placed  next  to  figures  for  figures  them- 
selves. The  following  abbreviations  have  been  used  exten- 
sively and  are  recommended:  — 

c.y.     —     cubic  yards 

s.y.     —     square  yards 

f.c.      —     cubic  feet 

s.f.      —     square  feet 

f.l.      —    linear  feet 

sqs.     —     squares  (100  sq.  ft.) 

$       —     when  placed  before  stands  for  the 
number  of  units 

%       —     when  placed  after  stands  for 

pounds 
Ddt.  —     deduct 

Concrete  Foundation  Wall 

Under  this  heading,  generally  speaking,  should  be  included 
all  concrete  walls  below  grade.  In  scaling  such  walls  the 
quantity  scaled  should  include  all  concrete  above  grade 
which  can  be  correctly  classed  as  a  part  of  the  foundation 
wall. 

For  example,  a  cellar  wall  may  extend  a  foot  or  more 
above  grade  before  reaching  the  level  of  the  first  floor,  yet 
the  part  above  grade  will  be  classed  as  foundation  wall 
along  with  the  part  of  this  wall  which  is  built  below  the 


12 


Estimating  Concrete  Buildings 


grade  level.  It  is  the  usual  practice  to  include  under  the 
term  foundation  walls  all  the  concrete  walls  which  are  below 
the  level  of  the  first  floor,  and  to  include  area  walls,  pit 
walls,  etc. 


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FIG.  3 


Fig.  3  represents  a  cross  section  and  plan  of  the  founda- 
tion wall  extending  around  a  reinforced  concrete  building 
having  a  length  of  160  feet  and  a  width  of  60  feet.  In  scaling 
the  quantity  of  concrete  in  this  foundation  wall  the  sections 
or  pieces  of  wall  should  be  considered  by  elevations  as 
follows  :  — 


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Estimating  Concrete  Buildings 


13 


It  will  be  noted  that  in  scaling  the  concrete  foundation 
wall  shown  above,  the  wall  on  the  side,  or  south,  elevation 
is  scaled  for  the  full  length  of  the  elevation.  The  quantity 
of  concrete  in  the  splayed  part  is  added  as  part  of  the 
foundation  wall.  The  concrete  in  the  7  piers  or  pilasters 
is  then  added,  the  dimensions  always  being  given  in  the 
order  of  length,  width  and  height.  Next  the  east  or  end 
wall  is  scaled  (progressing  anti-clockwise). 

In  the  case  of  the  ends,  in  order  to  avoid  doubling  the 
amount  of  material  in  the  corners,  the  inside  dimension 
is  scaled  instead  of  the  outside  "over  all"  dimension.  This 
dimension  should  be  set  down  in  the  length  column  to  read 
(60-1-f).  The  concrete  in  the  two  piers  or  pilasters  is  next 
added.  The  north  wall  is  scaled  similar  to  the  south,  and 
the  west  similar  to  the  east.  The  concrete  in  the  4  corner 
piers  is  then  added  and  the  scaling  for  the  foundation  wall 
is  complete. 

Concrete  Exterior  and  Interior  Columns 

i^U- 


4  corner  Coh. 

FIG.  4 


14 


Estimating  Concrete  Buildings 


Fig.  4  represents  a  part  cross  section  showing  the  typical 
exterior  columns  of  a  building  160  feet  long  and  60  feet  wide. 

Assuming  these  typical  columns  to  be  spaced  20  feet 
apart,  there  will  be  18  such  columns  in  the  building  and  4 
corner  columns.  The  scaling  of  the  quantity  of  concrete  in 
these  columns  will  appear  as  follows :  — 


J^ 

f 

2 

•^ 

fi 

^^ 

, 

// 

? 

-^ 

2 

/ 

4 

& 

, 

M 

t? 

r 

A 

sf 

<7C, 

/ 

/ 

^ 

^ 

ti 

/ 

•h 

/ 

- 

//? 

« 

r 

?  f 

V 

1  /> 

f-f 

't 

p 

j 

ff~ 

/ 

&-* 

-1-7 

a*i 

/ 

^  f 

^ 

/ 

^ 

fd 

T-\ 

*d 

^ 

- 

/< 

l\ 

;) 

c    , 

/ 

» 

.2 

^ 

s( 

, 

* 

f 

/ 

ft 

f 

^ 

I 

r^ 

V 

Cci 

\ 

** 

& 

/ 

^ 

•^ 

S~i 

^pf 

^ 

= 

$ 

j* 

4rl 

f 

f  . 

v 

J. 

T  , 

, 

& 

ft 

/ 

^ 

z 

^ 

/ 

t< 

ft 

6 

r 

T 

^ 

f^ 

£, 

B 

2,} 

'^ 

# 

y 

/9 

l& 

* 

/, 

& 

- 

r* 

^ 

£ 

ff 

^. 

, 

^ 

-i 

s 

*r 

I 

J 

\ 

Following  through  this  scaling  we  have  in  the 
column  the  number  18,  which  denotes  the  number  of 
typical  exterior  columns  in  each  story.  In  the  next  three 
columns  of  the  estimate  sheet  are  placed  the  length,  width 
and  height  respectively  of  the  columns  being  scaled. 

Each  of  the  four  corner  columns  has  both  exterior  faces 
of  the  same  dimension,  but  the  inside  corner  is  notched  out. 
This  complicates  the  expression  representing  the  cross  sec- 
tional area  of  the  column,  which  is  set  down  in  the  length 

and  width  columns  of  the  esti- 
mating sheet.  This  expression 
consists  of  two  parts.  The  first 
part  represents  a  rectangular 
column  and  the  second  part 
represents  the  area  of  the 
notched  portion  of  the  column 
which  is  to  be  deducted  from  the 
larger  area.  Corner  columns,  or 
any  irregular  columns  should  al- 
ways be  scaled  in  this  manner. 
The  second  story  columns 
should  be  scaled  similar  to  the 
first  story  columns  above 
discussed. 

As  only  the  concrete  brackets 
now  remain  to  be  scaled,  it  is 
necessary  merely  to  count  up 
the  number  of  brackets  and  to 
determine  the  approximate 


1- 

\ 

7: 

+  * 
(0  

to 

— 

4$ 

—  * 

» 

s 

s^ 

—  • 

/ 

-  — 

4-J  V  rods 
j^  ho  op  s  /?; 

1-7-4  MiX 

?0"dj3. 
-~\&-i0+rod5 
gthoops-irc 
i-ik-3  Mix 


FIG.  5 


Estimating  Concrete  Buildings 


15 


number  of  cubic  feet  of  concrete  in  one  bracket.  This  com- 
pletes the  scaling  of  concrete  in  the  exterior  columns. 

The  scaling  for  the  interior  columns  should  be  done  in  a 
similar  manner,  unless  they  happen  to  be  round  instead  of 
square. 

Assume  that  Fig.  5  represents  a  typical  interior  first  and 
second  story  column  of  a  building  in  which  there  are  14 
such  columns.  The  scaling  for  these  14  first  story  and  14 
second  story  columns  should  appear  as  follows :  — 


4«ii 


In  scaling  the  interior  columns,  the  second  column  on  the 
estimate  sheet  should  contain  the  number  of  identical 
members  being  scaled  (14  in  this  case).  As  these  interior 
columns  are  round,  it  is  not  possible  to  use  the  length  and 
width  columns  exactly  as  outlined  at  the  beginning  of  this 
chapter.  These  two  columns  should  contain,  however, 
figures  which  represent  the  cross  sectional  area  of  the 
member.  It  is  best  to  do  this  by  noting  the  diameter  of  the 
column,  enclosing  same  in  parentheses.  Immediately  follow- 
ing should  be  noted  in  square  feet  the  cross  sectional  area 
of  the  column.  The  height  column  should  contain  the  length 
of  the  member  from  the  floor  to  the  level  of  the  bottom  of 
the  drop  panel.  Next  is  noted  in  the  times  column  the 
number  of  column  heads  (usually  the  same  as  the  number  of 
columns)  and  in  the  length  and  width  columns  the  approxi- 
mate number  of  cubic  feet  of  concrete  in  the  head  which  is 
in  excess  of  the  shaft  already  scaled.  The  similar  tabulation 
of  the  upper  story  columns  completes  the  scaling  of  interior 
column  concrete. 

Concrete  Floor  Slabs  and  Roof  Slab 

Scaling  the  quantity  of  concrete  in  floor  and  roof  slabs 
is  very  simple.  As  in  scaling  the  concrete  for  beams  and 
columns,  the  dimensions  should  be  taken  off  in  the  order 
of  length,  width  and  height. 

For  instance,  assume  that  it  is  necessary  to  scale  the 
concrete  in  the  second  floor  slab  and  roof  slab  of  a  reinforced 
concrete  building  160  feet  long  and  60  feet  wide.  The  second 


16 


Estimating  Concrete  Buildings 


floor  slab  is  7^  inches  thick,  and  the  edge  of  the  slab  is  set 
back  2  inches  from  the  line  of  face  of  the  building.  There  is 
a  stair  well  opening  in  the  slab  18  ^  feet  long  and  10  feet 
wide.  The  roof  slab  is  6  inches  thick  and  has  no  opening. 
The  quantities  of  concrete  would  appear  as  follows :  — 


i±i 


It  will  be  found  in  first  practice  that  it  is  the  natural 
tendency  to  put  down  the  thickness  of  the  slab  in  the  width 
column  instead  of  in  the  last  or  height  column.  This  tendency 
will  be  overcome  quickly  if  the  estimator  remembers  that 
whether  it  is  beam,  column  or  floor  slab,  the  order  of  scaling 
dimensions  of  concrete  should  always  be  length,  width,  and 
height.  The  thickness  of  the  slab  is  a  very  important  dimen- 
sion and  should  be  accurately  tabulated  on  the  estimate 
sheet.  If  the  slab  thickness  is  5>£  inches,  the  fraction  tabu- 
lated in  the  height  column  should  be  ^J.  This  is  one  of  the 
very  few  instances  which  occur  in  scaling  concrete  work 
when  fractions  having  denominators  larger  than  12  are 
recommended. 


Concrete  Drop  Panels 

Drop  panels  which  occur  over  the  column  heads  of  flat 
slab  designs  should  be  considered  as  small  floor  or  roof  slabs 
when  being  scaled  for  estimate  purposes. 

The  quantity  of  concrete  in  the  drop  panels  shown  under 
the  floor  slab  and  roof  slab  in  Fig.  5  would  appear  on  the 
estimate  sheet  as  shown  below. 


;afl 


^ 


Concrete  Wall  Beams 

Under  the  heading  wall  beams  should  be  included  the 
curtain  walls,  parapet  beams,  and  other  similar  structural 
members.  In  Fig.  4  is  shown  a  typical  wall  beam  and  parapet 
beam  in  a  building  160  feet  long  and  60  feet  wide.  The 
exterior  columns  are  20  feet  apart.  The  concrete  in  the  wall 
beams  and  parapet  beams  will  appear  as  follows :  — 


Estimating  Concrete  Buildings 


17 


^ 

1 

,  , 

/I 

/) 

j#y 

/< 

M,1 

"T^   ' 

*1 

| 

T? 

K/ 

'Z<<6 

I?)  Y- 

-<5 

fi 

1 

4 

-  — 

-^ 

-^ 

-i1. 

Ti 

\( 

^i 

"1* 

g 

~ 

'? 

*^ 

. 

IF 

^r; 

?«' 

~~     . 

^ 

4' 

'  ^ 

r\ 

. 

^ 

f 

ft 

X 

<c 

*) 

s 

2 

fcC) 

^k 

g 

7 

j 

The  expression  within  the  braces  above  represents  the 
total  actual  length  of  wall  beam.  Within  the  braces  we  find 
two  expressions;  the  first  enclosed  in  brackets,  and  the  last 
in  parentheses  only.  The  first  of  these  represents  the 
perimeter  of  the  building,  and  the  second  the  total  length 
of  column  faces,  which  should  be  deducted  from  the 
perimeter  in  order  to  arrive  at  the  actual  total  length  of 
wall  beam.  The  parapet  is  scaled  in  a  similar  manner,  but 
no  deductions  are  made  except  for  overlapping  corners.  It 
will  be  found  that  errors  will  be  avoided  if  wall  beams, 
parapets,  etc.,  are  scaled  in  this  manner.  If  the  beams  are 
considered  individually,  omissions  of  entire  beams  are  very 
likely  to  occur  and  the  error  may  easily  be  passed  unnoticed. 


Interior  Floor  Beams 

Interior  floor  beams  are  usually  scaled  by  simply  noting 
in  the  description  column  the  location  or  index  number  of 

the  beam  or  beams. 

The  times  column  contains  the 
number  of  identical  beams,  and  the 
length,  width  and  height  columns  are 
used  according  to  the  method  set 
forth  throughout  the  preceding 
pages. 

The   height   of   a   beam    should 
always  be  taken  exclusive  of  the 
slab  thickness.  Beams  around  stair 
openings  should  be  treated  in  the 
FIG.  e  same  way,  except  that  sketches  of 

the  cross  section  of  the  beam  should  usually  be  made  in  the 
description  column  as  a  help  in  determining  the  formwork  as 
indicated  in  the  illustration  below.  For  instance,  if  we  have 
two  stair  well  beams  as  shown  in  Fig.  6,  the  quantities 
of  concrete  will  appear  as  follows :  — 


w- 

.. 

: 

- 

•? 

/- 

,', 

it 

'-?< 

t 

^ 

«-* 

>Z" 

Z3z 

Zi» 

Mi 

3* 

f-f 

V* 

* 

/ 

7.^: 

'* 

- 

0 

~  ' 

'X 

'4 

^ 

/ 

L. 

\ 

L 

*r 

r 

/?< 

'«. 

- 

'7 

^f 

-' 

t 

•; 

r 

*/ 

^ 

s 

XJ 

-if 

- 

18 


Estimating  Concrete  Buildings 


Partitions 

Concrete  partitions  are  scaled  in  the  same  manner  as 
interior  concrete  beams. 

In  the  description  column  should  be  noted  the  approximate 
location  or  character  of  the  partitions.  The  remaining 
columns  of  the  estimate  sheet  are  to  be  used  as  hereinbefore 
set  forth.  It  should  always  be  borne  in  mind  that,  in  this 
case,  the  thickness  of  the  partition  is  the  width  or  second 
dimension  scaled.  The  concrete  quantities  appear  below  for 
the  6-inch  concrete  partitions  shown  in  Fig.  6  and  occurring 
on  the  first  and  second  floors  of  a  building  having  a  story 
height  of  about  11  feet. 


Window  Sills  and  Copings 

Concrete  window  sills  and  copings  are  scaled  by  the 
linear  foot.  In  taking  off  the  quantity  of  each  the  work 
proceeds  by  elevations. 

For  instance,  in  the  description  column  should  appear  the 
words  "south  elevation,"  after  which  should  appear,  in  the 
times  and  length  columns,  the  number  and  length  of  the 
window  sills  or  coping  on  the  south  elevation.  The  east, 
north  and  west  elevations  should  then  be  considered  in  turn. 
A  cross-sectional  sketch  or  notation  as  to  size  of  sill  or  coping 
should  be  made  in  the  description  column,  as  a  help  in 
determining  the  correct  unit  price  per  linear  foot  when  the 
work  of  pricing  the  estimate  is  to  be  done.  The  following 
illustrates  the  proper  method  of  scaling  window  sills.  Should 
concrete  copings  occur  on  top  of  brick  parapet  walls,  similar 
methods  should  be  observed. 


Stairs  and  Landings 

Fig.  7  represents  the  flight  of  reinforced  concrete  stairs 
shown  in  Fig.  6. 


Estimating  Concrete  Buildings 


19 


In  order  to  scale  the  stairs,  count  the  number  of  nosings 
(18  in  this  case),  and  set  the  number  down  in  the  length 
column.  The  width  column  should  contain  the  length  of  each 


Jecffon  thru  Sfsfrs 

FIG.  7 

nosing  from  wall  to  outer  edge.  The  product  of  the  two 
dimensions  will  give  the  linear  feet  of  nosing  which  should 
be  taken  as  the  standard  of  measure  for  concrete  stairs. 

Landings  are  measured  by  the  square  foot  and  the  landing 
beams  may  be  neglected,  as  in  pricing  out  the  cost  of  the 
landing  per  square  foot  proper  allowance  is  made  for  the 
extra  cost  of  the  landing  beam.  The  thickness  of  the  landing 
slab  may  also  be  neglected  as  in  the  case  of  the  stairs. 
Concrete  stairs  and  landings,  unless  of  special  design, 
may  be  considered  in  this  manner  without  appreciable  error 
in  cost  estimating.  Below  is  given  the  proper  scaling  of  the 
concrete  stairs  and  landing  shown  in  Fig.  7  and  Fig.  6. 


/  ^_^ 

y*Q 

K- 

S> 

/ 

JjJ2 

rT7 

?r 

-7- 

y 

, 

p 

^ 

to 

... 

- 

fa 

3 

' 

4H' 

/  , 

i 

^ 

- 

\ 

<< 

i  i 

1 

/  1 

•r 

'j 

r 

-S-'1 

f 

Paving 

Concrete  paving  is  a  term  applied  to  an  unreinforced 
concrete  slab  resting  on  earth  fill,  such  as  a  basement  floor 
or  the  first  floor  of  a  building  where  no  basement  is  called 
for.  In  scaling  the  quantity  of  concrete  in  concrete  paving 
the  same  rules  are  observed  as  are  laid  down  for  a  concrete 
slab.  The  concrete  in  a  piece  of  paving  5  inches  thick  and 


20 


Estimating  Concrete  Buildings 


160  feet  long  by  60  feet  wide  would  appear  on  the  estimate 
sheet  as  follows :  — 


Granolithic  Finish 

Scaling  the  quantity  of  granolithic  finish  in  a  building  is 
done  at  this  stage  of  the  estimate  because  the  surfaces  having 
granolithic  finish  applied  to  them  have  already  been  scaled, 
and  determining  the  quantity  of  granolithic  finish  required 
is  simply  a  matter  of  referring  to  previous  dimensions.  For 
instance,  if  the  second  floor  slab  previously  scaled  is  to  be 
finished  with  a  granolithic  finish  of  the  "laid  after"  type, 
and  on  the  paving  above  an  integral  granolithic  finish  is 
called  for,  the  granolithic  finish  dimensions  would  appear 
on  the  estimate  sheet  as  follows :  — 


-  /* 

2 

H 

^1 

^ 

• 

A 

'-( 

S 

fV 

E 

• 

3 

"\ 

-/ 

A 

( 

ft 

r<? 

* 

4 

^ 

?-f 

1 

f 

^ 

rf'i 

/f 

/ 

£ 

/  jj 

'^ 

x2 

-x 

^, 

/ 

/ 

v>^ 

/^, 

4^ 

A 

T 

',( 

f 

^ 

r* 

rr 

^ 

; 

r< 

/ 

/i 

~if 

^ 

.  j 

* 

1 

„ 

<S 

V 

'/4 

^ 

. 

<? 

f 

£ 

' 

! 

r 

Carborundum  Rubbing 

The  area  of  the  surfaces  to  be  treated  with  carborundum 
rubbing  can  be  more  easily  determined  if  left  until  the  formed 
surfaces  have  been  determined.  This  will  be  taken  up  in 
another  part  of  the  chapter. 


IV.     FORMS 

If  the  foregoing  rules  have  been  carefully  followed  in 
regard  to  scaling  concrete,  the  work  of  determining  the 
amount  of  formwork  necessary  to  mould  the  concrete  may 
be  very  easily  accomplished  with  virtually  no  further  refer- 
ence to  the  drawings. 

In  writing  out  the  form  dimensions,  it  is  necessary  to 
refer  to  the  concrete  dimensions  and  copy  such  figures  as 
indicate  the  formed  surfaces.  As  but  three  columns  of  the 
estimating  sheet  are  needed  in  tabulating  the  dimensions 
for  formwork,  the  second,  or  times 9  column  is  left  blank  and 
the  remaining  three  columns  used  for  this  work.  Very  little 
description  is  needed  in  writing  out  formwork  dimensions, 
since,  in  order  to  learn  the  character  of  the  work  formed, 


Estimating  Concrete  Buildings 


21 


it  is  necessary  only  to  turn  back  to  the  concrete  scaling 
corresponding  to  the  formed  surfaces  in  question.  Enough 
description  should  be  given  in  the  description  column  to 
make  it  easy  to  identify  the  form  dimensions  with  the  con- 
crete scaling. 

• 

Forms  for  Exterior  and  Interior  Footings 

The  form  dimensions  for  the  concrete  footings  as  scaled 
from  Fig.  2  are  shown  properly  written  out  below. 


— 

- 

<^?v 

_ 

S 

/ 

/ 

/ 

•X 

•7 

f, 

?> 

'l 

f  . 

fo 

? 

? 

f, 

1  > 

''*.. 

/ 

^ 

? 

1 

'T 

* 

3 

f: 

/ 

/• 

rV 

t 

•*/ 

1 

/^ 

f 

*) 

? 

$ 

K 

The  first  number  written  out  is  22,  and  represents  the 
number  of  footings  being  formed.  The  second  dimension 
is  19^,  and  represents  the  perimeter  of  the  lower  block. 
The  third  dimension  is  Ij,  and  represents  the  height,  in 
feet,  of  the  lower  block.  On  the  next  line  below  occur  the 
dimensions  of  the  formed  surfaces  of  the  upper  block  of  the 
exterior  footings  treated  in  the  same  manner.  The  interior 
footings  are  treated  in  the  same  way.  The  product  of  these 
figures  as  shown  will  give  the  surfaces  of  concrete  in  the 
footings  which  must  be  provided  with  forms,  and  is  to  be 
priced  out  in  the  estimate  as  "surface  measurement." 


Forms  for  Foundation  Walls 

In  scaling  the  forms  for  foundation  walls  it  must  be 
remembered  that  both  sides  of  the  wall  are  to  be  formed, 
hence  the  first  figure  written  down  must  be  the  figure  2. 
The  figures  shown  below  represent  the  correct  tabulation 
of  the  form  dimensions  for  the  concrete  foundation  wall 
as  scaled  from  Fig.  3. 


i2 

*-4 

;.. 

•;. 

s 

/^ 

/^ 

;«, 

,,, 

?r 

•r? 

7, 

o. 

- 

> 

*<-* 

2 

» 

7 

^^ 

^ 

^ 

.-., 

^  V 

Jv 

^? 

s 

') 

j 

? 

j 

5 

r 

<< 

f  / 

tsr 

_/ 

%c, 

^ 

f, 

^x 

,s 

^ 

" 

'7 

,( 

^ 

' 

X 

? 

•/, 

? 

1 

X 

X, 

.^ 

<f- 

^ 

'A 

^ 

7 

ft 

\ 

S 

_^4 

^> 

rrc 

•r 

'-Tl 

<./ 

'^ 

^ 

7 

S) 

^ 

7 

y< 

,_ 

' 

f^ 

'* 

7 

r'^ 

p. 

/ 

fl. 

7 

x 

A 

,  / 

<7 

7 

ty 

.. 

7 

y/ 

^. 

^ 

TT 

/ 

- 

X/i- 

/i 

>. 

f-, 

1 

r./? 

F 

•V 

,, 

/ 

-' 

_, 

First  the  figure  2  denotes  that  two  sides  are  formed.  Next 
in  order  is  stated  the  length  of  the  wall  to  be  formed,  and 


22 


Estimating  Concrete  Buildings 


last  the  height  of  the  formwork.  Both  the  length  and  height 
dimensions  of  the  wall  are  taken  directly  from  the  concrete 
scaling.  The  piers  are  projections  on  the  face  of  the  wall; 
and,  as  the  face  of  the  pier  is  already  measured  when  the 
face  of  the  wall  is  taken,  it  is  necessary  to  add  only  the 
surfaces  of  the  edges  of  the  piers»to  complete  the  foundation 
wall  forms.  The  corner  piers  do  not  increase  the  amount  of 
formed  surface  and  may  be  neglected  in  writing  out  the 
form  dimensions. 

Forms,  however,  must  be  provided  for  the  edge  of  the 
paving  concrete  and  this  is  usually  added  to  the  foundation 
wall  forms. 


Forms  for  Exterior  and  Interior  Columns 

In  writing  out  the  form  dimensions  for  exterior  columns, 
and  other  rectangular  or  notched  columns,  the  same  rules 
are  followed  as  have  been  laid  down  for  footing  forms. 
There  are  but  three  dimensions  or  numbers  to  write  down 
on  the  estimate  sheet,  viz.,  number  of  columns,  perimeter 
of  column  and  height  of  the  surface  formed.  These  dimen- 
sions may  be  taken  directly  from  the  concrete  scaling. 

The  forms  for  round  columns  and  column  heads  are 
usually  made  of  sheet  steel  or  iron.  Hence,  instead  of  deter- 
mining the  square  feet  of  formed  surface,  it  is  necessary 
only  to  list  the  number  of  columns  formed,  their  diameter 
and  height. 

The  forms  for  the  brackets  are  determined  by  simply 
listing  the  number  of  brackets  and  determining  the  approxi- 
mate number  of  square  feet  in  one  bracket.  The  formed 
surface  of  the  bracket  should  be  kept  separate  from  the 
main  column  forms,  as  the  unit  price  of  labor  is  at  least 
double  for  this  work.  Below  will  be  found  the  form  dimen- 
sions for  the  exterior  and  interior  columns  as  taken  from 
the  concrete  scaled  from  Fig.  4  and  Fig.  5. 


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Estimating  Concrete  Buildings 


23 


Forms  for  Floor  Slabs  and  Roof  Slab 

In  writing  out  the  forms  for  flat  slabs,  it  is  necessary 
only  to  determine  the  area  of  the  slab.  The  length  and  width 
dimensions  of  the  slab  are  taken  directly  from  the  scaled 
dimensions  of  the  concrete  without  reference  to  the  plans. 
The  areas  of  the  bottoms  of  the  drop  panels  should  be 
deducted  after  reference  to  the  scaling  of  the  concrete  in 
the  drop  panels.  If  the  slab  forms  are  for  the  beam  and 
girder  type  of  floor,  the  area  of  the  slab  is  determined  as 
above  and  then  the  beam  bottoms  are  deducted  from  the 
slab  areas. 

To  deduct  the  beam  bottoms  it  is  necessary  to  refer  to 
the  scaled  dimensions  of  the  floor  beams  and  girders  and 
select  those  dimensions  which  represent  the  bottom  surfaces 
of  all  beams  occurring  in  the  floors.  Deductions  for  openings 
are  made  from  form  quantities  only  when  the  area  equals 
or  exceeds  25  square  feet.  Even  in  the  latter  case,  the  full 
opening  should  not  be  deducted,  since  an  allowance  must 
be  made  for  the  formwork  required  to  form  the  concrete 
at  the  edge  of  the  opening.  The  forms  for  the  concrete  floor 
and  roof  slab  scaled  on  page  7  have  been  properly  written 
out  below,  and  comparisons  should  be  made  with  the  con- 
crete scaling  in  order  fully  to  understand  the  method. 


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Drop  panels  are  part  of  the  floor  slab  concrete,  and,  as 
the  areas  of  the  bottoms  of  the  drop  panels  have  been  de- 
ducted from  the  floor  slab,  it  is  necessary  to  restore  this 
area  again  under  this  heading.  The  formed  areas  of  the 
edges  are  also  to  be  added  to  the  area  of  the  bottoms.  No 
deduction  is  made  for  the  opening  in  the  bottom  of  the  drop 
panel  form  where  the  column  head  joins  the  drop  panel. 
The  dimensions  written  out  below  represent  the  formed 
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24 


Estimating  Concrete  Buildings 


Forms  for  Wall  Beams 

Properly  to  write  out  the  forms  for  wall  beams,  curtain 
walls,  parapet  beams,  etc.,  it  is  necessary  to  observe  the 
rules  laid  down  for  foundation  walls. 

Both  sides  are  formed,  hence  the  necessity  for  placing 
the  figure  2  before  the  dimension  representing  the  linear 
feet  of  wall  beam.  The  height  of  a  wall  beam  is  figured  from 
the  inside  vertical  height.  As  this  leaves  the  outside  edge 
of  the  floor  slab  without  forms,  it  is  necessary  to  add  an 
area  of  formed  surface  equal  to  the  perimeter  of  the  building 
multiplied  by  the  thickness  of  the  floor  slab.  This  takes 
account  of  all  exposed  surfaces  to  be  formed,  except  the  pro- 
jecting sides  of  the  concrete  in  the  columns  at  the  floor  level 
for  a  height  equal  to  the  thickness  of  the  floor  slab  only. 
This  is  so  slight  that  it  may  be  neglected.  The  forms  for  the 
parapet  are  written  out  following  the  principles  outlined 
for  wall  beams.  The  forms  for  the  wall  beams  and  parapet 
in  Fig.  4  have  been  properly  shown  below  and  comparisons 
with  the  corresponding  concrete  scaled  from  Fig.  4  should 
be  made. 


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Forms  for  Interior  Floor  Beams 

If  no  sketches  appear  in  the  description  column  of  the 
scaling  of  the  concrete  in  the  floor  beams,*  it  is  assumed  that 
a  slab  of  uniform  thickness  rests  upon  the  beams. 

The  number  of  beams  and  the  length  of  each  are  first 
written  down  as  for  other  concrete  members  of  similar 
structure.  As  the  scaled  dimension  of  the  beam  height  is 
taken  to  the  bottom  of  the  slab  only,  it  is  quite  simple  to 
compute  mentally  the  sum  of  the  two  side  dimensions  plus 
the  bottom  dimension.  This  represents  the  formed  area  of 
one  linear  foot  of  beam  and  should  be  written  in  the  fourth, 
or  width  column  of  the  estimate  sheet.  The  product  of  these 
dimensions  will  give  the  area  of  the  formed  surfaces  of  the 
interior  floor  beams. 

If  accompanying  sketches  show  that  other  formwork  is 
necessary  completely  to  form  the  beam,  proper  additions 
should  be  made  to  take  care  of  it.  The  formed  surfaces  of 


*See  Interior  Floor  Beams,  p.  17. 


Estimating  Concrete  Buildings 


25 


the  concrete  as  scaled  in  the  floor  beams  shown  in  Fig.  6 
are  somewhat  irregular,  as  they  occur  at  stair  openings. 
The  quantities  of  this  form  work  appear  below. 


*£ 


Forms  for  Partitions 

In  writing  out  the  formed  areas  of  concrete  partitions, 
the  same  rules  are  observed  as  for  other  wall  forms. 

Openings  are  not  deducted  unless  the  area  of  the  opening 
equals  or  exceeds  25  square  feet.  The  formed  areas  for  the 
concrete  partitions  shown  in  Fig.  6  are  given  below. 


Forms  for  Window  Sills,  Copings,  Stairs  and  Landings 

No  formed  areas  are  written  out  for  window  sills,  copings, 
stairs  or  landings.  This  departure  from  the  usual  practice 
is  justified  because  the  unit  prices  per  linear  foot  of  this 
work  are  made  up  to  include  the  cost  of  concrete,  forms, 
reinforcement  and  finish.  This  unit  price  is  usually  a  stand- 
ard one  for  each  type  of  work,  and  is  applied  directly  to  the 
linear  feet  of  work  as  scaled  under  the  heading  of  concrete  on 
the  estimate  sheets. 


Formed  Surfaces  —  Carborundum  Rubbed 

Referring  again  to  the  subject  of  carborundum  rubbing,  — 
when  the  form  dimensions  are  written  out,  it  is  very  simple 
to  determine  the  square  feet  of  surface  to  be  rubbed. 

This  may  be  done  very  quickly  by  picking  out  from  the 
formed  areas  the  surfaces  which,  according  to  specification, 
must  be  treated  with  carborundum.  It  will  be  found  most 
convenient  to  leave  the  work  of  determining  the  area  of 
concrete  surfaces  to  be  rubbed  until  after  the  extension  of  the 
form  dimensions  has  been  completed.  The  surface  measure- 
ments of  all  formed  surfaces  will  then  be  found  in  the 
quantity  column  reduced  to  square  feet,  and  the  total  area 
of  the  rubbed  surfaces  may  be  quickly  determined. 


26  Estimating  Concrete  Buildings 

V.    REINFORCEMENT 

Scaling  the  quantity  of  reinforcement  in  a  concrete 
building  is  a  process  by  which  the  tonnage  of  steel  bars  is 
obtained. 

It  is  not  necessary  to  make  a  schedule  of  the  bars  in  the 
entire  building,  a  process  entailing  a  large  amount  of  tedious 
work.  Footing  reinforcement  is  usually  scaled  by  listing  the 
size  of  the  bars  first,  then  the  number  of  bars  needed,  and 
finally  the  length  of  the  bar  itself.  Oftentimes  it  will  be  found 
convenient  to  compute  the  number  of  pounds  of  reinforce- 
ment in  a  footing  and  then  multiply  by  the  number  of  foot- 
ings. 

Reinforcement  in  foundation  walls  may  be  figured  at  the 
number  of  pounds  per  square  foot  of  wall.  Column  reinforce- 
ment is  usually  taken  off  the  plans  in  detail;  the  size,  number 
of  bars  and  the  length  of  the  bars  being  taken  off  in  regular 
order.  Slab  reinforcement  is  almost  always  computed  on 
the  square  foot  basis,  and  all  beam  reinforcement  by  the 
number  of  pounds  per  linear  foot  of  beam.  Curtain  wall  and 
partition  reinforcement  is  computed  by  the  number  of 
pounds  per  square  foot  of  reinforced  surface. 

In  computing  reinforcement  on  the  square  foot  and  linear 
foot  basis,  care  must  be  taken  to  allow  for  all  secondary 
steel,  laps  for  bond,  stirrups,  construction  bars,  waste,  etc. 
It  will  require  careful  practice  to  scale  reinforcement  accu- 
rately by  this  method,  which,  however,  once  thoroughly 
understood,  will  be  found  very  reliable  and  rapid. 

Reinforcement  is  listed  in  the  same  order  as  the  forms. 
The  different  types  may  be  easily  grouped  for  pricing.  The 
fac-simile  of  an  estimate  reproduced  farther  on  gives  a 
correct  representation  of  the  manner  in  which  reinforcement 
should  be  scaled  for  estimating  purposes. 

VI.    EXCAVATION 

General  or  Steam  Shovel  Excavation 

General  excavation  is  the  term  applied  to  the  process  of 
removing  the  earth  for  basements,  or  cutting  down  the 
grade  to  the  paving  level. 

General  excavation  does  not  include  the  excavation  for 
footing  holes  below  the  paving  level,  or  other  small  excavated 
areas  where  hand  work  entirely  must  be  used.  Steam  shovels, 
scraper  diggers,  or  hand  work  may  be  used  in  general 


Estimating  Concrete  Buildings  27 

excavation;  and  when  the  quantity  is  scaled  for  estimating 
purposes,  notation  should  be  made  of  the  probable  method 
to  be  employed  in  doing  the  work.  In  scaling  dimensions  for 
general  excavation,  the  order  should  be  the  same  as  for 
scaling  concrete  work,  viz.,  length,  width  and  height;  and 
these  should  be  written  down  in  the  proper  columns  of  the 
estimate  sheet.  Proper  allowance  should  also  be  made  for 
slope  of  the  earth  work  outside  of  the  exterior  footings  when 
the  length  and  width  dimensions  are  scaled.  If  the  general 
excavation  is  done  by  hand,  vertical  sheeting  may  be  used 
instead  of  excavating  to  a  slope.  All  these  conditions  should 
be  noted  in  the  description  column  when  the  scaling  is  done. 

Footing  Excavation 

The  labor  of  removing  earth  for  footing  holes,  pits, 
trenches,  etc.,  is  nearly  always  done  by  hand  and  should  be 
described  on  the  estimate  sheet  as  footing  excavation. 

In  scaling  the  quantities  for  footing  excavation,  the  nature 
of  the  soil  to  be  removed  should  be  noted  as  well  as  the 
location  of  the  footing  hole  in  respect  to  the  plans.  Footing 
holes  excavated  to  a  depth  exceeding  4  feet  should  be 
scaled  net;  that  is,  add  but  6  inches  to  the  length  and  width 
dimensions  of  the  footing  for  the  size  of  the  excavated  hole. 
This  allows  for  the  thickness  of  the  sheeting  lumber  generally 
used  in  connection  with  footing  excavation  exceeding  4  feet, 
but  not  exceeding  10  feet,  in  depth.  In  scaling  footing 
excavation  when  the  depth  is  less  than  4  feet,  no  sheeting  is 
used;  but  proper  allowance  is  made  in  scaling  dimensions 
to  allow  for  the  slope  of  the  earth  work.  When  sheeting  is 
used  for  footing  excavation,  the  sheeting  usually  serves  as 
formwork  for  the  lower  block  of  concrete  in  the  footing. 

Backfill 

Backfill  is  a  term  applied  to  the  labor  of  rehandling 
excavated  material  after  the  footings  have  been  placed  and 
it  becomes  necessary  to  fill  in  around  the  footing,  wall  or 
other  foundation  work. 

This  quantity  usually  equals  the  amount  of  earth  removed 
in  excavating  for  the  footing,  as  the  amount  of  earth  which 
is  left  after  the  footing  hole  is  properly  backfilled  must  be 
rehandled  and  disposed  of  in  some  other  way.  Where  the 
earth  work  is  a  large  part  of  the  job  operations,  the  backfill 


28  Estimating  Concrete  Buildings 

and  general  disposition  of  excavated  material  should  be 
carefully  considered. 

Sheeting 

Sheeting  is  estimated  by  the  square  feet  of  surface 
measurement  of  earth  retained.  As  the  form  dimensions  are 
written  out  from  the  scaled  dimensions  of  the  concrete  work, 
so  are  the  sheeting  dimensions  written  out  from  the  scaled 
dimensions  of  the  excavation.  No  allowance  is  made  for  the 
distance  the  sheeting  penetrates  the  ground  below  the 
bottom  of  the  excavated  hole  or  for  the  distance  above  the 
top  of  the  earth  work  retained. 


VII.    MASONRY 

Brick  Work 

Brick  work,  where  more  than  4  inches  thick,  is  estimated 
by  the  cubic  foot. 

In  order  to  determine  the  cubic  feet  of  brick  work  in  a 
wall,  the  dimensions  are  scaled  in  the  same  manner  as 
outlined  for  Concrete  Partitions.  In  scaling  the  brick  work 
in  the  exterior  walls  of  a  building,  the  work  should  be 
done  by  elevations,  and  adequate  description  be  given 
to  make  it  easy  to  check  over  the  work  to  determine  whether 
any  part  has  been  omitted.  The  quantities  should  contain 
the  actual  number  of  cubic  feet  of  brick  work  to  be  built 
and  no  more.  All  openings  should  be  deducted  exactly  as 
they  are  shown,  and  no  allowances  made  in  the  quantity  to 
take  care  of  work  which  may  be  more  or  less  expensive  to 
construct  than  the  average  unit  price  will  pay  for.  After  the 
actual  cubic  feet  of  brick  work  in  a  building  is  determined, 
the  unit  price  should  then  be  made  up  to  correspond  with 
the  class  of  work  to  be  built. 

Brick  Veneer 

Brick  veneer  is  usually  laid  up  4  inches  thick,  and  is  so 
noted  in  the  description  column,  together  with  other  nota- 
tions regarding  the  character  and  location  of  the  work. 

As  brick  veneer  is  estimated  by  the  square  foot  in  scaling 
the  quantity,  it  is  necessary  to  determine  the  length  and 
height  only  of  the  work,  using  columns  Number  4  and 
Number  5  in  which  to  write  down  these  dimensions.  The 


Estimating  Concrete  Buildings  29 

work  should  proceed  by  elevations,  as  in  the  case  of  scaling 
other  classes  of  brick  work. 

Terra  Cotta  Partitions 

Partitions  built  from  hollow  terra  cotta  blocks  are  esti- 
mated by  the  number  of  blocks  laid  up  in  a  wall. 

As  nearly  all  hollow  terra  cotta  blocks  have  a  face 
measurement  of  one  square  foot  each,  the  number  of  blocks 
in  the  terra  cotta  wall  corresponds  to  the  number  of  square 
feet  in  the  face  of  the  partition.  In  scaling  the  square  feet  of 
terra  cotta  partition  it  is  necessary  to  observe  the  same 
methods  as  were  laid  down  for  scaling  Concrete  Partitions. 
Notation  should  always  be  made  in  the  description  column 
regarding  the  type  of  block  specified  and  the  thickness 
of  the  partition.  All  deductions  should  be  accurately  made. 
It  may  be  stated  here  that  the  mortar  joints  in  the  work 
offset  the  usual  breakage  of  the  blocks  in  transit  and  no 
allowance,  therefore,  need  be  made  for  either  mortar  joints 
or  breakage. 

VIII.    PLASTERING 

Plastering  is  measured  by  the  square  yard  of  surface 
measure. 

The  dimensions  making  up  the  quantity  are  usually 
taken  directly  from  the  scaled  dimensions  of  the  terra  cotta 
partitions,  ceilings,  walls,  or  other  surfaces  in  a  manner 
similar  to  that  in  which  carborundum  rubbed  surfaces  are 
determined.  In  the  description  column  are  noted  the  number 
of  coats  called  for,  the  kind  of  cement  specified,  and  other 
items  helpful  in  deciding  upon  proper  unit  prices. 

IX.    STEEL  SASH 

In  estimating  steel  sash,  the  important  points  to  consider 
are  size  of  opening,  uniformity  of  size  and  type,  percentage 
of  ventilation,  and  operation. 

The  description  column  should  contain  information 
relative  to  all  these  points.  In  scaling  the  size  of  the  opening 
the  number  of  identical  sash  should  first  be  listed  in  the 
second  column  of  the  estimate  sheet.  The  length  and  height 
of  the  openings  should  follow  in  the  third  and  fourth  columns 
respectively.  The  sash  openings  should  be  scaled  by  eleva- 
tions, since,  by  this  method,  omissions  of  any  magnitude 
are  quickly  noted  when  the  dimensions  are  extended. 


30  Estimating  Concrete  Buildings 

X.    GLASS  AND  GLAZING 

After  noting  in  the  description  column  the  kind  and  size 
of  glass  specified,  it  is  a  simple  matter  to  determine  the 
number  of  square  feet  of  glass  required  to  glaze  the  sash. 

For  estimating  purposes,  it  is  sufficiently  close  to  assume 
that  90%  of  the  sash  area  is  made  up  of  glass.  Accordingly, 
the  glass  required  is  usually  carried  out  on  the  estimate 
sheet  as  90%  of  sash  area. 

XI.  DOORS,  FRAMES  AND  HARDWARE 

In  listing  the  doors,  frames  and  hardware  in  a  building, 
the  doors  should  be  considered  individually  or  by  types. 

The  location  and  character  of  the  door  should  be  noted 
in  the  description  column  together  with  notations  as  to 
frame  and  hardware.  In  writing  down  the  size  of  the  door, 
the  width  should  be  first  considered  and  the  height  last. 
For  instance,  a  door  2  feet  and  8  inches  wide  by  6  feet  and 
8  inches  high  should  appear  on  the  estimate  sheet  as  f  x 
•§-.  The  number  of  doors  of  a  kind  is  written  down  in  the 
summary  column  as  the  scaling  is  done. 

XII.  LIGHT  IRON  WORK  AND  MISCELLANEOUS 

IRON 

No  special  ruling  can  be  set  down  governing  the  scaling 
of  light  iron  work  for  general  estimating  purposes. 

The  estimator  should  list  intelligently  all  such  material, 
and  at  the  same  time  endeavor  to  scale  the  dimensions  in  a 
manner  which  will  result  in  the  quantity  being  reduced  to 
the  proper  basis  for  pricing  out.  Pipe  hand  rails  should  be  in 
linear  feet;  safety  stair  treads  in  linear  feet;  steel  inserts  by 
the  piece;  cast  iron  scuppers  by  the  piece;  and  curb  angle 
guards  in  linear  feet  at  so  many  pounds  per  foot,  etc.,  etc. 
It  is  also  customary  to  carry  out  in  the  total  column  a  certain 
sum  of  money  decided  upon  in  the  judgment  of  the  estimator 
as  adequate  to  cover  miscellaneous  iron  work  which  is  not 
shown  or  called  for  on  plans  or  in  specifications,  but  which 
must  inevitably  be  supplied  by  the  builder. 

XIII.    ROOFING  AND  FLASHING 

The  roofing  dimensions  are  usually  taken  directly  from  the 
scaling  of  the  concrete  for  the  roof  slab. 


Estimating  Concrete  Buildings  31 

This  is  generally  full  measure,  since  the  parapet  beams 
reduce  the  roofing  area  slightly  below  the  slab  area.  But,  as 
roofing  is  measured  in  units  of  squares  (100  square  feet), 
the  result  is  sufficiently  accurate.  In  scaling  the  roofing  area, 
it  is  first  necessary  to  note  in  the  description  column  the  kind 
of  roofing  required,  and  the  guarantee. 

Flashings  are  a  part  of  the  roofing  contract  and  should  be 
scaled  immediately  following  the  roofing.  Base  and  cap 
flashings  are  estimated  by  the  linear  foot,  and  notation 
should  be  made  of  the  kind  of  metal  specified  together  with 
the  number  of  inches  in  width  required  to  flash  one  linear 
foot.  Metal  gravel  strip  should  be  scaled  in  the  same  manner. 
Conductor  boxes  are  estimated  by  the  piece  and  should  be 
listed  in  the  summary  column  accompanied  by  proper 
description. 

XIV.    PAINTING 

Painting  of  walls  and  ceilings  is  measured  by  the  square 
yard,  and,  as  in  estimating  the  amount  of  carborundum 
rubbing,  the  painted  surfaces  may  be  determined  by  referring 
to  the  extended  dimensions  of  the  form  areas  of  the  concrete 
work. 

Other  painted  work  such  as  brick  walls,  terra  cotta  walls, 
etc.,  may  be  determined  readily  by  referring  to  the  quantities 
already  scaled  for  this  work  and  the  total  painted  areas  then 
reduced  to  square  yards  and  written  down  in  the  sumruary 
column. 

Painting  steel  sash  and  doors  is  also  measured  by  the 
square  yard.  To  determine  the  amount  of  painting  on  the 
steel  sash  and  doors  of  a  building,  reference  should  be  made 
to  the  scalings  for  the  sash  and  doors,  and  the  flat  areas 
should  be  added  together  just  as  if  the  entire  areas  were  to 
be  painted  like  a  door.  Double  these  areas,  since  doors  and 
sash  are  painted  both  sides.  Then  divide  this  amount  by  9. 
The  result  will  be  the  square  yards  of  painting  which 
should  appear  in  the  summary  column  of  the  estimate 
sheet. 

Painting  light  iron,  miscellaneous  iron,  etc.,  is  usually  a 
small  item  and  is  not  figured  on  a  square  yard  basis,  but 
rather  by  the  judgment  of  the  estimator.  The  amount  of 
money  allowed  for  this  depends  entirely  upon  the  miscel- 
laneous iron  to  be  painted,  and  each  job  must  be  considered 
individually. 


32  Estimating  Concrete  Buildings 

XV.    ENGINEERING,  PLANS,  ETC. 

Sometimes  the  builder  is  called  upon  to  include  in  his 
estimate  the  cost  of  preparing  designs  and  plans  for  the 
work  to  be  estimated.  The  percentage  of  cost  varies  with 
the  type  of  building  and  the  skill  of  the  engineers  doing  the 
work.  Ordinarily  the  plans  of  a  regular  reinforced  concrete 
factory  can  be  prepared,  from  the  surveys  to  the  finished 
drawings  and  details,  for  3%  of  the  net  cost  of  the  com- 
pleted structure. 

XVI.    CLEAN  UP  THE  JOB  AT  COMPLETION 

The  estimator  must  allow  a  sum  of  money  sufficient  to 
cover  the  cost  of  cleaning  up  the  job  at  completion,  removing 
debris  from  the  site,  washing  windows,  and  leaving  the  job 
"broom  clean." 

XVII.    LIABILITY  INSURANCE 

An  item  should  be  included  in  the  estimate  which  will 
cover  the  cost  of  carrying  liability  insurance  for  the  period 
of  the  job. 

The  rate  for  this  varies  in  different  localities  and  with 
different  contractors.  The  percentages  may  run  as  low  as 
3%  of  the  amount  expended  for  labor;  or,  on  the  other 
hand,  it  may  run  as  high  as  12  or  14%  of  the  labor  costs. 
As  the  labor  expense  involved  in  constructing  a  regular 
reinforced  concrete  building  amounts  to  about  one-third  of 
the  total  cost  of  the  building,  the  amount  of  money  to  be 
allowed  for  liability  insurance  premiums  is  easily  determined 
when  the  rate  is  known.  For  instance,  assume  that  the  rate 
is  6%  of  the  labor  and  the  total  estimate  amounts  to  $62,000 
without  profit.  If  this  building  is  a  regular  reinforced  con- 
crete factory,  the  labor  involved  would  be  about  one-third 
of  $62,000,  or  approximately  $21,000.  Computing  6%  of 
$21,000,  we  have  $1,260.  The  amount  of  money  carried  in 
the  estimate  for  liability  insurance  premiums  could  well  be 
taken  at  $1,250. 

XVIII.    WATCHMAN 

In  order  to  estimate  the  cost  of  employing  a  watchman 
while  a  building  operation  is  going  on,  it  is  first  necessary 
to  determine  approximately  the  number  of  weeks  required 
to  construct  the  building.  This  decided  upon,  it  is  a  matter 


Estimating  Concrete  Buildings  33 

of  computing  the  expense  of  employing  a  watchman  for  this 
length  of  time  at  a  proper  weekly  wage. 

XIX.     SUPERINTENDENCE,  JOB  OVERHEAD, 
OFFICE  EXPENSES,  ETC. 

Under  this  head  must  be  included  all  the  expense  attached 
to  maintaining  a  job  office,  including  the  job  superintendent. 
It  is  usual  custom  to  determine  the  amount  of  this  expense 
for  one  week  and  to  multiply  this  amount  by  the  number 
of  weeks  the  office  must  be  maintained.  Under  the  head  of 
superintendence,  office,  etc.,  must  be  figured  the  wages  of 
the  following  men: 

Job  superintendent 

Timekeeper 

Chief  office  clerk 

Tool  boy 

On  unusually  large  jobs,  the  office  force  will  consist  of  more 
men  than  above  listed,  while  on  a  very  small  job  the 
personnel  may  be  cut  down  by  arranging  to  have  the  chief 
clerk  act  as  timekeeper  in  connection  with  his  other  duties. 
The  cost  of  telephones,  stationery,  railroad  fares,  freight 
on  supplies,  building  and  dismantling  office,  etc.,  must  be 
considered.  These  are  items  which  may  be  easily  estimated 
at  too  low  a  figure.  Proper  consideration  should  be  given 
to  every  expense  entering  into  overhead  if  the  estimate  is  to 
be  an  accurate  one  in  which  allowance  has  been  made  for 
proper  and  competent  job  management. 

XX.  SUNDRIES 

It  often  occurs  that  estimates  are  made  from  plans  not 
completely  finished  or  from  poorly  prepared  drawings. 
The  uncertainty  attached  to  making  estimates  from  such 
plans  makes  it  advisable  to  conclude  the  estimate  with  an 
item  for  sundries,  the  amount  of  which  should  be  deter- 
mined in  the  estimator's  judgment  as  being  adequate  to 
protect  his  estimate  against  over-runs  due  to  his  having 
omitted  some  work  implied  but  not  shown  or  called  for. 
The  amount  of  this  item  should  be  based  on  a  percentage 
of  the  total  estimated  cost  not  including  profit,  and  usually 
runs  from  2%  to  5%,  according  to  the  condition  of  the  plans. 
It  is  very  seldom  that  an  estimate  should  be  prepared  with- 


34  Estimating  Concrete  Buildings 

out  any  allowance  for  over-runs  due  to  unforeseen  condi- 
tions. 

XXI.  PROFIT 

The  percentage  of  profit  is  figured  on  the  total  cost  of 
the  work  including  labor,  materials,  etc. 

It  may  be  a  very  low  percentage  or  it  may  be  very  high, 
depending  entirely  on  the  basis  on  which  the  contractor 
is  operating  his  business. 

Eight  per  cent  is  considered  a  very  low  profit,  and  the 
contractor  must  do  a  large  volume  of  business  and  keep 
his  hired  organization  well  employed  in  order  to  be  success- 
ful at  this  rate.  Percentages  of  profit  will  run  from  8%  to 
15%,  and  sometimes  higher.  For  ordinary  estimating  pur- 
poses, 10%  may  be  assumed  as  a  fair  profit  for  the  builder 
of  reinforced  concrete  buildings,  unless  the  estimated  total 
cost  runs  under  $50,000,  in  which  case  12%  profit  should  be 
added  to  the  estimate. 

EXEMPLIFICATION  OF  PRECEDING 
PRINCIPLES 

Figures  8a  and  8b  present  the  plan  and  cross  section  of  a 
typical,  small,  reinforced  concrete  factory,  the  parts  of  which 
have  been  already  scaled  in  detail  in  the  previous  pages  of  this 
chapter.  The  necessity  for  condensation  has  made  the 
explanations  brief.  Hence  the  reader's  initiative  must  be 
depended  upon  for  further  study  of  the  subject  at  hand  and 
for  the  discovery  of  the  best  ways  of  attacking  problems 
in  estimating  not  here  covered.  The  principles  outlined, 
however,  have  been  tested  by  many  years  of  use  in  a  large 
Boston  Company  operating  extensively  in  the  reinforced 
concrete  field.  The  many  advantages  to  be  gained  by  their 
application  have  been  conclusively  proved.  A  fac-simile  of 
the  completed  estimate  for  the  building  illustrated  in  Figures 
8a  and  8b  is  shown  herewith.  It  will  be  noted  that  the  scalings 
are  identical  with  those  discussed  on  the  previous  pages.  The 
quantities  have  been  extended,  unit  prices  affixed,  and  the 
totals  carried  out,  thus  constituting  as  a  whole  the  finished 
estimate  for  the  construction  of  the  building  proper.  The 
determination  of  unit  prices  is  considered  in  Part  II. 


Estimating  Concrete  Buildings 


35 


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r~T — ' 

i   A    ! 


i — i""1. 
i 


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X 

5 

0,4 


36 


Estimating  Concrete  Buildings 


Estimating  Concrete  Buildings 


37 


FAC-SIMILE  OF  THE  COMPLETED  ESTIMATE 
FOR  A  CONCRETE  BUILDING 

(Compare  Figures  8a  and  8b) 


38 


Estimating  Concrete  Buildings 


THE   COMPLETED   ESTIMATE   (Continued) 


r  = 


9 


is 


£  — 


Estimating  Concrete  Buildings 


THE   COMPLETED  ESTIMATE   (Continued) 


1 


&£ 


H 


t~£\ 


'*  I 


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40 


Estimating  Concrete  Buildings 


THE  COMPLETED  ESTIMATE  (Continued} 


Estimating  Concrete  Buildings 


41 


THE  COMPLETED  ESTIMATE   (Concluded) 


42  Estimating  Concrete  Buildings 


PART  II 
DETERMINING  UNIT  PRICES 

I.  GENERAL  CONSIDERATIONS 

The  two  principal  elements  which  control  unit  prices  in 
general  are  labor  and  material. 

In  order  to  arrive  at  a  correct  unit  price  for  a  certain 
building  operation,  it  is  essential  to  know  very  closely  how 
much  labor  is  involved  in  performing  a  unit  of  this  work, 
and  also  how  much  material  will  be  required.  The  items  of 
labor  and  material  must  be  estimated  separately  and  then 
combined,  the  two  together  constituting  the  unit  price  to 
be  used  in  the  estimate.  Every  step  involved  should  be 
carefully  analyzed  and  correct  values  calculated  for  the 
labor  and  material  in  each  one. 

The  unit  prices  used  in  the  estimate  sheets  which  have 
been  illustrated  in  this  text  have  been  based  on  the  labor 
rates  and  material  costs  prevailing  in  New  England  at  the 
time  of  its  preparation  (August,  1919).  Since,  however,  costs 
vary  greatly  in  different  localities  and  with  changing  markets 
for  labor  and  material,  the  unit  prices  shown  here  should 
be  viewed  with  caution  for  estimating  purposes.  They  are 
given  for  showing  method,  not  as  offering  a  table  of  results. 
The  volume  of  material  and  labor  being  priced  has,  too,  an 
important  bearing  on  the  unit  price.  In  short,  it  should 
always  be  borne  in  mind  that  a  correct  unit  price  for  esti- 
mating purposes  should  be  established  after  study  of  the 
circumstances  and  conditions  peculiar  to  the  particular 
job  under  consideration.  It  cannot  be  obtained  in  any  other 
manner. 

At  the  time  when  this  paper  goes  to  press,  common 
laborers  receive  an  average  wage  of  50  cts.  per  hour.  Carpen- 
ters, masons  and  other  skilled  building  workers  receive  90 
cts.  per  hour.  The  unit  costs  shown  on  the  accompanying 
estimate  sheets  are  made  up  in  accordance  with  the  above 
labor  rates.  Adjustments  should  be  made  accordingly. 


Estimating  Concrete  Buildings  43 

II.  CONCRETE 

Foundation  Concrete 

The  unit  price  for  the  concrete  in  foundations  is  reached 
by  first  ascertaining  the  amount  of  material  and  labor 
necessary  to  make  one  cubic  yard  of  concrete  mixed,  in 
this  case,  in  the  proportion  of  1-3-6. 

Experience  has  shown  that  to  estimate  the  quantity  of 
cement,  sand  and  crushed  stone  from  the  tables  set  forth 
in  text  books,  which  seldom  allow  for  waste,  is  to  encounter 
a  shortage  of  materials.  It  will  be  noted  that  in  working 
out  the  amounts  of  material  in  the  following  calculation, 
proper  allowance  has  been  made  for  inevitable  waste. 

Concrete  —  per  cubic  yard  (1-3-6  mix) 

Cement,  1TV  bbls ,@    $2.77  =      $3.05 

Sand,    Yz  cu.  yd @      1.95  =          .98 

Cr.  stone,  1&  tons @      2.75  =        3.58 

Plant 2.10 

Labor,  mixing  and  placing 1.75 

Total  cost  per  cu.  yd $11.46 

(Use  $11.50  for  unit  price.) 

The  price  of  cement  above  is  that  obtained  from  cement 
dealers  ($2.84  per  barrel/. 0.6.  cars,  job).  In  this  price  is  an 
allowance  for  4  cement  bags  which,  if  returned  to  the  dealer 
in  good  condition,  will  be  credited  at  10  cts.  each  or  40  cts.  per 
barrel.  A  cash  discount  of  5  cts.  per  barrel  is  also  allowed  if 
payments  are  promptly  made.  If  advantage  of  both  these 
credits  (45  cts.)  is  taken,  the  net  cost  of  the  cement  becomes 
$2.39  per  barrel. 

Unloading  and  storing  the  cement  in  a  cement  shed  costs 
usually  25  cts.  per  barrel.  Tests  must  be  made  by  the  Cement 
Testing  Bureau  to  ascertain  the  quality  of  the  cement, 
for  which  an  average  charge  of  3  cts.  per  barrel  is  made.  The 
loss  of  credits  due  to  injury  to  bags  in  transit  and  to  the 
cost  of  freight  on  returned  bags  amounts  to  about  10  cts.  per 
barrel  of  cement  purchased.  Allowance  being  made  for  the 
above  charges,  the  price  of  cement  becomes  $2.77  per  barrel 
and  it  is  this  figure  which  is  used  in  working  out  the  cost  of 
concrete. 

The  following  calculation  shows  in  detail  how  this  price 
is  determined. 


44  Estimating  Concrete  Buildings 

Cement  —  Dealer's  quotation,  f.o.b.  cars  job $2.84 

Credit  for  bags 40 

Cash  discount 05  .45 

$2.39 

Unloading  and  storing  cement 25 

Testing  cement 03 

Loss  and  freight  on  empty  bags     ..'-.* 10 

Total  cost  per  bbl $2.77 

Sand  —  Dealer's  quotation,  f.o.b.  cars  job $1.75 

Unload  and  handle  into  bins 20 

Total  cost  per  cu.  yd $1.95 

Crushed  stone  —  f.o.b.  cars  job      $2.50 

Unload  and  handle  into  bins 25 

Total  cost  per  ton    ? $2.75 


Plant  Cost 

As  a  certain  amount  of  machinery,  chutes,  runways, 
towers,  etc.,  are  required  in  the  process  of  placing  concrete, 
an  allowance  must  be  made  in  the  unit  price  for  the  labor  of 
erecting  and  dismantling  this  "plant  work,"  as  it  is  commonly 
called.  Allowance  must  also  be  made  for  plant  material 
purchased  or  rented  for  the  duration  of  the  job.  This  item 
varies  with  the  size  and  type  of  the  job.  It  may  run  as  low 
as  $1.00  per  cubic  yard,  and,  in  especially  difficult  jobs, 
may  run  as  high  as  $3.00  or  more  per  cubic  yard  of  concrete 
placed.  A  plant  cost  of  $2.10  per  cubic  yard  has  been  in- 
cluded in  the  unit  price  of  the  concrete  estimated  herein, 
and  the  sub-divisions  of  this  cost  are  listed  below. 

Plant  cost  per  cubic  yard  of  concrete: 

Labor  Material  or  rental  charge 

Towers $00.20  $00.20 

Temporary  bldgs 12  .15 

Bins  for  aggregate 10  .20 

Mixer  and  motor 06  .14 

Canvas  and  chutes 05  .35 

Runway,  staging 

and  small  tools 14  .24 

Fuel,  power  and  water   ...  .15 

Material  and 

Labor    .            ....  $00.67  Rentals     $1.43  Total  per  cu.yd.  $2.10 


Estimating  Concrete  Buildings  45 

The  average  labor  cost  of  mixing  and  placing  concrete 
in  a  reinforced  concrete  building  with  common  labor  at 
50  cts.  per  hour  is  about  $1.75  per  cubic  yard  when  modern 
plant  equipment  is  used  on  the  job.  A  saving  of  25  cts.  on  the 
labor  cost  and  25  cts.  on  the  plant  cost  per  cubic  yard  is 
usually  made  in  placing  paving  concrete,  making  the  unit 
for  this  class  of  work,  50  cts.  less  than  for  other  concrete  work 
of  a  similar  mix. 


Column  and  Slab  Concrete 

The  unit  price  of  concrete  mixed  in  the  proportions  of 
1-2-4  and  1-1^-3  is  made  up  in  a  similar  way.  No  change 
is  made  in  the  quantity  of  sand,  crushed  stone,  labor  and 
plant.  The  cement  quantity  alone  is  changed.  The  compu- 
tation for  1-2-4  and  1-1  j^-3  concrete  follows. 

Concrete,  per  cubic  yard  (1-2-4  mix) 

Cement,  If  bbls @    $2.77  =      $4.62 

Sand,  y*  cu.  yd @      1.95  =          .98 

Cr.  stone,  l^r  tons @      2.75  =        3.58 

Plant 2.10 

Labor  mixing  and  placing 1.75 

Total  cost  per  cu.  yd $13.03 

(Use  $13.00  for  unit  price.) 

Concrete,  per  cubic  yard  (1-1^-3  mix) 

Cement,  2  bbls @    $2.77  =      $5.54 

Sand,  X  cu.  yd @      1.95  =          .98 

Cr.  stone,  1-&  tons @     2.75  =        3.58 

Plant 2.10 

Labor  mixing  and  placing 1.75 


Total  cost  per  cu.  yd $13.95 

(Use  $14.00  for  unit  price.) 

Window  Sills 

The  unit  price  of  concrete  window  sills  of  approximately 
standard  size  usually  runs  close  to  72  cts.  per  linear  foot, 
including  concrete  forms,  reinforcement  and  finish.  The  price 
of  72  cts.  per  linear  foot  is  made  up  as  follows: 

Concrete      @  50  cts.  cu.  foot  =$00.27^ 

Formwork @  25  cts.  sq.  foot  =         .25 

Reinforcement @    5  cts.  Ib.  =        .07  j^ 

Carborundum  rubbing  (outside) .12 


Totalcostperlin.fi.      : $00.72 


46  Estimating  Concrete  Buildings 

Stairs  and  Landings 

The  cost  of  constructing  reinforced  concrete  stairs,  using 
rates  of  labor  and  materials  as  previously  noted,  is  about 
$1.50  per  linear  foot  of  nosing.  Landings  will  cost  about 
75  cts.  per  square  foot.  These  unit  prices  include  all  concrete, 
forms,  reinforcement  and  cement  finish  necessary  to  complete 
the  stairway.  No  safety  treads  or  hand  rails  are  included. 


Granolithic  Finish 

Granolithic  finish  1  inch  thick  laid  after  the  slab  concrete 
has  set  will  cost  about  11  cts.  per  square  foot  for  material  and 
labor.  The  unit  price  is  made  up  as  follows: 

1-inch  Granolithic  finish,  laid  after,  — per  1,000  sq.ft. 

Cement,  12#  bbls @    $2.77   =    $34.63 

Peastone,  4  tons @      3.00   =      12.00 

Labor  to  pick  and  clean  floor  preparatory  to 
laying  finish,  mix  and  lay  grano.  finish  in- 
cluding plant  costs  and  protect  while  dry- 
ing    65.00 

Total  cost  per  1,000  sq.  ft $111.63 

(Use  11  cts.  per  sq.  ft.  for  unit  price.) 

Note:  No  sand  is  required  in  granolithic  finish. 

If  the  granolithic  finish  is  laid  before  the  concrete  in  the 
slab  has  become  thoroughly  dried  out,  the  finish  is  called 
an  integral  finish.  In  estimating  a  finish  of  this  kind,  since 
the  thickness  of  the  granolithic  finish  is  included  in  the  slab 
concrete  quantities,  the  unit  price  should  contain  only  the 
labor  cost  of  the  cement  finisher's  time  and  the  cost  of  the 
extra  cement  used  in  the  top  part  of  the  slab  which  forms 
the  finish,  and  the  increased  cost  of  using  peastone  instead 
of  ordinary  crushed  stone.  The  unit  price  for  integral 
granolithic  finish  is  made  up  as  follows: 

1-inch  Granolithic  finish  —  laid  integral  —  per  1,000  sq.ft.  per  bbl. 

Extra  cement,  10  bbls @  $2.77  =  $27.70 

Labor,  finisher's  time 30.00 

Extra  cost  of  peastone,  4  tons     .    .    .    .@       .25  per  ton  =      1.00 

Total  cost  per  1,000  sq.  ft $58.70 

(Use  6  cts.  per  sq.  ft.  for  unit  price.) 

Cinder  Concrete 

The  unit  of  cinder  concrete  crickets  placed  on  the  roof  to 
form  proper  slope  to  downspouts  has  been  worked  out  in 
detail  as  follows: 


Estimating  Concrete  Buildings  47 

Cinder  Concrete  —  per  cu.  yd. 

Cement,  1  bbl @    $2.77   =  $2.77 

Cinders,  1  cu.  yd 1.50 

Plant  costs .    .  2.50 

Labor,  mix  and  place  to  slope 2.25 

Total  cost  per  cu.  yd $9.02 

(Use  $9.00  for  unit  price.) 

Carborundum  Finish 

The  cost  of  finishing  concrete  surfaces  with  carborundum 
stone  and  cement  varies  greatly  with  different  contractors. 
A  good  finish  may  be  obtained  by  going  over  the  surface  of 
the  concrete  twice  at  a  total  cost  of  about  7>£  cts.  per  square 
foot  of  surface  treated.  The  unit  price  is  made  up  as  follows : 

Carborundum  rubbing — 2  coats  —  per  1,000  sq.ft. 

Labor,  1st  rub $40.00 

Labor,  2nd  rub       30.00 

Cement  used,  #  bbl @    $2.77    =  1.38 


Total  cost  per  1,000  sq.  ft $71.38 

(Use  7>4  cts.  per  sq.  ft.  for  unit  price.) 


III.    FORMS 

General 

In  working  out  a  unit  price  for  formwork  it  is  very 
important  to  know  how  many  times  the  forms  can  be  used 
without  remaking.  If  it  is  possible  to  use  the  forms  twice, 
one-half  the  cost  of  the  lumber  should  be  charged  against 
the  unit  for  each  use.  If  the  forms  are  used  three  times,  a 
lumber  charge  of  one-third  the  cost  of  the  lumber  is  included 
in  the  unit  price,  and  so  on.  The  cost  of  erection  and  stripping 
the  formwork  remains  uniform  for  each  use,  but  some 
saving  is  made  on  making  when  the  forms  are  used  more 
than  once.  In  forming  one  square  foot  of  concrete  surface, 
about  3  board  feet  of  lumber  are  used  in  building  the  form- 
work.  Hence,  if  the  forms  are  used  but  once,  the  material 
charge  in  the  unit  price  will  be  the  cost  of  3  board  feet  of 
lumber.  If  the  formwork  is  used  twice,  it  will  be  necessary 
to  make  a  material  charge  of  only  1  *4  board  feet  of  lumber, 
and  so  on.  Some  salvage  of  the  lumber  is  usually  made  at 
the  completion  of  the  job,  except  where  the  formwork  is 
very  complicated  and  lumber  is  virtually  ruined,  in  which 


48  Estimating  Concrete  Buildings 

case  no  salvage  is  realized.  Ordinarily,  however,  a  saving 
of  about  15%  of  the  cost  of  the  lumber  is  realized  at  the 
close  of  a  job. 

A  certain  amount  of  machinery  is  required  with  which 
the  form  work  is  constructed  on  the  job.  This  consists  princi- 
pally of  a  saw  mill  and  motor,  small  tools,  nails,  etc.  This 
is  the  "plant  cost,"  and  seldom  amounts  to  more  than  1  ct. 
per  square  foot  of  concrete  surface  formed.  The  labor  in- 
volved in  making,  erecting  and  stripping  the  f ormwork  varies 
with  the  complexity  of  the  work,  but  seldom  costs  less  than 
7  cts.,  or  more  than  15  cts.,  per  square  foot  of  concrete 
surface  formed.  The  cost  of  the  labor  of  forming  a  concrete 
cornice  or  other  similar  work  will  be  much  more  than  this 
maximum. 


Form  Lumber 

The  unit  costs  for  the  formwork  on  the  estimate  sheets 
shown  herewith  have  been  worked  out  with  lumber  at  $60 
per  M,  f  .o.b.  cars  at  the  job.  Adding  to  this  $2.50  per  M  to 
cover  the  cost  of  unloading  and  handling  the  lumber  at  the 
job,  the  price  becomes  $62.50  per  M.  The  building  will 
probably  require  a  set  of  forms  for  one  complete  story,  and, 
with  a  small  amount  of  remaking,  these  forms  may  be  used 
for  forming  the  second  or  top  story.  This  having  been 
decided  upon,  it  follows  that  the  unit  price  should  contain  a 
material  charge  equal  to  the  cost  of  1^  board  feet  of 
lumber.  This  material  charge  is  maintained  throughout  the 
unit  prices  for  formwork  so  long  as  two  uses  are  reckoned 
on.  The  determination  of  unit  prices  for  the  formwork  used 
in  the  illustrative  estimate  are  shown  below. 

The  common  labor  is  figured  at  50  cts.,  and  carpenters' 
work  at  90  cts.  per  hour. 

Footing  Forms 

Lumber:  1^  board  feet     .     @  $62.50  per  M    =   $00.0938 
Deduct  salvage 0150     .0788 


Plant  cost 0100 

Labor,  make,  erect  and  strip 0800 


Total  cost  per  sq.  ft $00.1688 

(Use  17  cts.  for  unit  price.) 


Estimating  Concrete  Buildings  49 

Foundation  Wall  Forms 

The  unit  price  for  foundation  wall  forms  may  be  figured 
similar  to  footing  forms,  with  the  exception  that  the  labor 
will  cost  about  9  cts.  instead  of  8  cts.  per  square  foot.  This 
change  adds  1  ct.  per  square  foot  to  the  unit  price,  making 
the  unit  price  for  foundation  wall  forms  18  cts.  per  square 
foot. 

Exterior  Column  Forms 

Lumber:  1}£  board  feet    .     @  $62.50  per  M    =    $00.0938 
Deduct  salvage 0150     .0788 

Plant  costs 0100 

Labor,  make,  erect  and  strip 1175 


Total  cost  per  sq.  ft $00.2063 

(Use  2054  cts.  for  unit  price.) 

Bracket  Forms 

Lumber:  1^  board  feet @  $62.50  per  M  =     $00.0938 

(no  salvage  allowed) 

Plant 0100 

Labor,  make,  erect  and  strip 2350 

Total  cost  per  sq.ft. $00.3388 

(Use  33^  cts.  for  unit  price.) 

Interior  Column  Forms  (Round  Steel) 

Rental  of  steel  column  forms,  each $15.00 

Labor,  erect,  strip  and  handle 5.00 


Total  unit  cost,  each $20.00 


Flat  Slab  Floor  and  Roof  Forms 

Lumber:  1^  board  feet     .    @  $62.50  per  M  =   $00.0938 

Deduct  salvage 0150  .0788 


Plant 0100 

Labor,  make,  erect  and  strip 0775 


Totalcostpersq.fi $00.1663 

(Use  16>£  cts.  for  unit  price.) 


50  Estimating  Concrete  Buildings 

Drop  Panel  Forms 

Lumber:  1>£  board  feet @  $62.50  per  M     =   $00.0938 

(no  salvage  allowed) 

Plant 0100 

Labor,  make,  erect  and  strip 1075 


Total  cost  per  sq.  ft $00.2113 

(Use  21  cts.  for  unit  price.) 

Wall  Beam  Forms 

Lumber:  Inboard  feet    .    @  $62.50  per  M   =   $00.0938 

Deduct  salvage .0150         .0788 

Plant 0100 

Labor,  make,  erect  and  strip .    .     .0975 


Total  cost  per  sq.  ft $00.1863 

(Use  18X  cts.  for  unit  price.) 

Floor  Beam  Forms 

The  unit  cost  of  floor  beam  forms  works  out  quite  closely 
to  the  cost  of  the  wall  beam  forms,  the  only  difference 
being  an  increase  of  about  >£  ct.  per  square  foot  in  the  labor 
charge.  This  increase  makes  it  necessary  to  use  19c  as  a 
unit  price  for  floor  beam  forms.  Should  the  floor  be  what 
is  known  as  a  beam  and  slab  type  of  floor  the  average 
labor  cost  of  making,  erecting  and  stripping  the  forms, 
measuring  beams  and  slab  together  will  be  about  8tf  cts.  per 
square  foot.  This  would  make  the  unit  cost  of  beam  and 
slab  floor  forms  about  17 ^  cts.  per  square  foot  if  the  forms 
are  used  twice. 


Partition  Forms 

Lumber:  1^  board  feet   .    @  $62.50  per  M     =  $00.0938 

Deduct  salvage 0150         .0788 

Plant 0100 

Labor,  make,  erect  and  strip 1375 

Total  cost  per  sq.  ft $00.2263 

(Use  22>^  cts.  for  unit  price.) 


Estimating  Concrete  Buildings  51 

IV.     REINFORCEMENT 

The  labor  of  cutting,  bending  and  placing  reinforcement 
will  cost  from  $8.00  to  $20.00  per  ton,  depending  upon  the 
size  of  the  bar,  the  amount  of  bending  required,  and  the 
position  in  which  the  bars  must  be  finally  placed.  In  the 
average  concrete  building  it  is  safe  to  assume  that  a  flat 
rate  of  $14.00  per  ton  will  cut,  bend  and  place  the  rein- 
forcement in  the  building.  The  unit  price  used  in  the  accom- 
panying estimate  of  4><  cts.  per  pound  is  made  up  as  follows: 

Steel  Reinforcement 

Reinforcement  f.o.b.  cars,  job,  per  ton $68.00 

Unload  and  pile  on  job 3.00 

Cut,  bend  and  place,  including  wire,  etc 14.00 


Total  cost  per  ton $85.00 

(Use  4><  cts.   per  Ib.  for  unit  price.) 


CONCLUSION 

It  should  be  borne  in  mind  that  the  preceding  brief  dis- 
cussion of  methods  of  determining  unit  prices  makes  no 
pretense  of  being  other  than  an  outline  sketch  of  a  subject 
whose  exhaustive  treatment  might  well  occupy  a  good-sized 
volume.  Its  aim  has  been  to  indicate  the  proper  direction 
of  methods  to  be  used,  and  to  supply  a  sufficient  number  of 
illustrations  to  offer  a  clear  exemplification  throughout.  The 
judgment  and  experience  of  the  estimator,  in  any  given 
instance,  must  be  relied  upon  to  evaluate  the  influence  of 
modifying  elements  of  time,  place  and  special  circumstance. 


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